In some wireless local area networks (WLANs), different stations may transmit frames of different modulations types. For example, the IEEE-Std 802.11, 1999 Edition (ISO/IEC 8802-11: 1999) (“802.11”) set of standards allows coexistence of different formats of physical layer (PHY) protocol data units (PPDUs), or frames, in the same frequency channel. The various formats may differ, for example, in the respective sizes of the transmitted frames.
Network stations may use a channel access mechanism and a control mechanism to protect transportation of packets over the network, e.g., to avoid collision of frames. For example, a station may wait for the channel to be clear before transmitting the next frame. One solution may be to utilize a request-to-send/clear-to-send (RTS/CTS) mechanism, including setting a network allocation vector (NAV) to reserve the wireless medium for a predetermined period of time. However, such a protection method may cause significant overhead by taking up part of the available bandwidth and/or power for transmission of management frames. In addition, a network station that is in a power-save mode may not receive the RTS/CTS frames.
It will be appreciated that for simplicity and clarity of illustration, elements shown in the figures have not necessarily been drawn to scale. For example, the dimensions of some of the elements may be exaggerated relative to other elements for clarity. Further, where considered appropriate, reference numerals may be repeated among the figures to indicate corresponding or analogous elements.